1. E-beam Characterization: a primer Part 1
Phys 590B
April 2, 2014
Matthew J Kramer

2. Why and Which Method E-beam characterization E-beam Instruments
IT IS the only reliable means for microstructural and microchemical analysis!
E-beam Instruments
Surface
SEI
From mm to nm, surface information only
BSE
Surface Z distribution
Topography
Transmission
Diffraction contrast
Microns to atoms
Crystallography
Both types can utilize the various spectroscopes

3. Forest or the Leaves

4. What do you need to know? Surface scanning
Loose powders to polished surfaces
Large depth of field
Morphology will effect spectroscopy

5. Transmission Microscopy
Region of interest needs to be electron transparent
~10 – 100 nm, depending on Z
How you thin can matter
Significantly higher resolution
Very different imaging contrast used

6. The SEM E beam is accelerated by a large voltage
Lens forms a fine probe
Rastered across the sample
SEI
BSE

7. Imaging Secondary Electrons Backscattered Electrons Very near surface
Strongly Z dependent
Interactions at a depth
Co-Sm-Fe alloy

8. Crystallography
BSE can be induced to channel along crystallographic planes Electron Backscattered Diffraction (EBSD)

9. Si dendrites in Al matrix

10. e interactions Auger electrons
Two views of the Auger process. (a) illustrates sequentially the steps involved in Auger deexcitation. An incident electron creates a core hole in the 1s level. An electron from the 2s level fills in the 1s hole and the transition energy is imparted to a 2p electron which is emitted. The final atomic state thus has two holes, one in the 2s orbital and the other in the 2p orbital. (b) illustrates the same process using spectroscopic notation, KL1L2,3.

11. e interactions C and higher Z
E-beam energy must exceed the binding energy

12. Depth: 0.002 - 0.01 m (2-10 nm) 5-20 atom layers
Auger e’s vs X-rays
Counter yield
Auger e’s low energy
Require a high vacuum
Very near surface
0.01 x 0.01 x m
(10 x 10 x 2 nm )
200 x 200 m
Sample being analyzed
1 m3
XPS
AES
EDS
Depth: m (2-10 nm) 5-20 atom layers
NOTE: Scaling is only approximate

13. Detecting and Quantifying X-rays
Solid State detectors
Energy Dispersive Spectroscopy (EDS)

14. Detecting and Quantifying X-rays
Wavelength Dispersive Spectroscopy
Much higher energy resolution

15. Quantification and Spatial Resolution
Average Z and E dependent
Requires stable e-beam source
Requires standardization
Requires known geometry
i.e., flat, parallel surface
1 µm

16. Auger
EDS KV
Al-K
Ge-L Ge Al 20 15 10 5

17. JEOL 5910lv Resolution (SEI) Magnification Probe Current Image modes:
3.0 8 mm wd
Magnification
18-300,000 x
Probe Current  
1pa  1 microamp
Image modes:
SEI
3 Backscatter
Topo
Compo
Shadow
EDS
Line scans
mapping

18. JEOL 5910lv Poor Vacuum mode:
Resolution mm working distance
Backscattered mode only in the poor vac  mode
Adjustable chamber pressure Pa
Tungsten filament with automatic adjustments Beam Blanked in “Freeze” mode
Alignments and conditions automatically and individually saved for each user
Specimen Chamber and Stage:
5 axes (X 125mm range, Y 100mm range, Z 43mm range, T 10 to 90 range, R 360 endless)
Maximum specimen size 7” with full coverage
Specimen position graphical indicator as well as chamber camera
Absorbed current ( Specimen current ) measured
Image memory selectable to 1,280 x 960 x 8 bits Can frame average  up to 255 frames Image storage formats BMP, TIFF or JPEG. 
We recommend BMP with merged text.

19. JEOL JXA-8200 Superprobe combined WDS/EDS
5 wavelength-dispersive spectrometers, 10 crystals
B through U
four 140 mm Rowland circle
one 100mm Rowland circle
EDS, 10 mm2 Si(Li) crystal, Be window
Na through U
Software
quantitative analysis
compositional mapping
phase analysis
integrated WDS/EDS operation.

20. Overall Capabilities Electron Optical and Vacuum Systems
W or LaB6 electron source
Acceleration voltage kV
Useable beam current to 10-5A
Pneumatically driven Faraday cup for beam current measurement (serves as beam blanking)
Turbomolecular vacuum pump
All functions controlled through central computer system
Imaging Capabilities
Secondary electron detector
Backscattered electron detector with composition/topography mode
10 user selectable scan speeds
Magnification 40x to 300,000x
Optimal imaging resolution 6nm
Dedicated 18 inch flat panel display for electronic images
Optical microscope for reflected light observation of sample
Optical system coaxial with electron beam
High resolution color video mini camera
Automatic optical focus device

21. Sample Preparation Maximum sample size Stage travel Stage tracking
150 x 150 x 50mm
4 x 1in. diameter samples
Stage travel
x = 100mm, y = 90mm, z = 3mm
Stage tracking
< ±1μm
Requires flat, well polished surface
Standardization
Elemental or line compounds

22. Element Mapping

23. JAMP7830F Auger Microprobe
Schottky field emission gun
0.5 to 25kV beam voltage
10-11 to 1x10-7 A current
Minimum probe size:
4 nm in SEM mode,
10 nm in Auger mode
Chamber pressure
5 x 10-8 Pa (3 x torr)
Stage movement:
X,Y mm, Z + - 6mm
Normal sample size:
12mm dia. 5mm thick

24. JEOL 7830F Schematic View
Key Components that produce High Energy Resolution and Reliable KE Values
JEOL 7830F AES Advantages & Capabilities ( HSA vs CMA, and FE vs LaB6 )

25. Elemental Mapping
Nb-Cu metal-metal composite

26. High Energy Resolution AES Chemical State Map:
Cuo vs Cu2O (D E = 0.9 eV)
Cu2O
Cuo
Red = Cuo Green = Cu2O
SEM

27. Chemical Shifts O Gas Capture Study CrOx CrOx Cro Cro
This sample was ion etched to remove all contamination and left in UHV at 3 x torr 14 hr. This reveals the reactive nature of “clean” surfaces. O
14 hr - end
Gas Capture Study
CrOx
CrOx
O hr - start
Cro
Cro
Reactive Nature of the Clean Surface of a Co-Ni-Cr Alloy

28. Limitations of Auger Electron Spectroscopy
Cannot detect hydrogen or helium
Destructive depth profiles.
Samples must be small and compatible with high vacuum.
Elemental quantization depends on instrumental, chemical, and sample related factors.
Chemical information is depended on quantity and element
Most sample surfaces are contaminated—must be cleaned by ion etching

29. Sample Preparation Best if sample is parallel polished
Best sample size:
< 10 mm dia.
< 3 mm thick
Please no potting of sample in plastic matrix
For very small samples consult with us first
Samples that are used in some type of process, need to be in proper form before processing
Remember ---- do not touch the samples with your hands!

30. Conclusions 1st determine what you need to know
i.e., grain size or just average chemistry
How precise do your measurements need to be?
Will dictate sample preparation, obtaining standards etc.
WDS vs EDS or is BSE good enough
What elements are possibly present, including impurities?
Are there overlaps? WDS vs EDS
Chemistry of the surface or of the bulk?
XPS and SAM vs SEM
Decide which instrument(s) will be needed
Discus techniques and sample preparation first with staff
Not with your classmates (unless they are an expert)!
Keep an open mind
It is not unusual that your preconceived notions are wrong
But artifacts are possible
How does grinding and polishing affect the composition and possibly microsctucture
Is your sample sensitive to air, moisture etc.
How do these results mesh with other bulk measurements?
Microscopy is a powerful tool, but one of many tools, it should be complimented with other techniques when appropriate.
XRD, SQUID etc.

31. SEM vs TEM Imaging Physics is completely different
SEM – scattered electrons from the surface (secondary or backscattered)
TEM – elastically and in elastically transmitted electrons through a thin foil.
Imaging
diffraction

32. Interaction with the Sample
Mean free path
Measure of the probability of an electron interacting with the sample
How to thin your sample and how thin to make it
Affect diffraction contrast
Determine accuracy of your spectroscopy

33. Electron Diffraction

34. Diffraction Patterns Captured using an area detector
Sample can be tilted

35. Improving the Diffraction Information
SADPs contain only rather imprecise 2D crystallographic information because the Bragg conditions are relaxed for thin specimens and small grains within the specimen

36. Convergent beam electron diffraction
Region sampled limited to the probe size
Contains both the elastic and inelastic scattered electrons

38. These patterns will aid in tilting and precisely setting image conditions